1. Field of the Invention
The present invention relates to a data communication system, more particularly, to a data communication system in which two communication offices are provided in a 1:1 correspondence, and each office includes a main communication apparatus communicated with another main communication apparatus through a channel, a stand-by communication apparatus communicated with another stand-by communication apparatus through another channel, and a switching controller; the switching controllers in the both communication offices independently operating. Each switching controller switches between the main and stand-by communication apparatuses in its own communication apparatus in response to an event to be switched. In addition, each switching controller switches between the main and stand-by communication apparatuses in its own communication apparatus in response to a change of a switching status in another communication office.
2. Description of the Related Art
In a variety of data communication systems, to improve the reliability and availability, a redundant system configuration in which a main communication apparatus and a stand-by communication apparatus are provided, is extensively been adopted. In such data communication systems, a switching between the main communication apparatus and the stand-by communication apparatus is required, and a variety of switching methods are known. Note, the switching method depends upon the configuration of the data communication system.
In a data communication system in which a pair of communication offices are provided in a 1:1 correspondence, and each office includes a main communication apparatus communicated with another main communication apparatus through a channel, a stand-by communication apparatus communicated with another stand-by communication apparatus through another channel, a switching between the main communication apparatus and the standby communication apparatus is independently carried out at both of the communication offices. However, the prior art switching suffers from a long switching time, a complex procedure, etc., when difference in the switched statuses of the communication offices occur. The prior art switching for the above data communication system will be described later in more detail with, reference to the drawings.